Field of the Invention
The present invention relates to an information processing apparatus used in ophthalmological diagnosis and treatment, an operation method thereof, and a computer program.
Description of the Related Art
Examination of the eye is widely performed for early diagnosis and treatment of lifestyle diseases and diseases which are primary causes of loss of eyesight. The scanning laser ophthalmoscope (SLO), which is an ophthalmological apparatus that employs the principle of confocal laser scanning microscopy, performs high speed raster scanning of a subject's eye with a laser beam, which is measurement light, and acquires a high-resolution planar image of the fundus from the intensity of returning light.
In confocal laser scanning microscopy, detecting only light that has passed through an aperture (pinhole) enables an image to be formed just using returning light of a particular depth position (focal point), and therefore images with higher contrast than those obtained by fundus cameras and the like can be acquired. An apparatus that obtains such high-contrast planar images will hereinafter be referred to as an SLO apparatus, and a planar image obtained thusly is referred to as an SLO image.
In recent years, increased beam diameter of measurement light in SLO apparatuses has enabled acquisition of SLO images of the retina, with improved horizontal resolution. However, the increased beam diameter of the measurement light has led to deterioration of the S/N ratio and of the resolution of the SLO image during acquisition of SLO images of the retina, due to aberration of the eye being examined. An adaptive optics SLO apparatus has been developed to counter the deterioration of S/N ratio and improve resolution of the SLO image. The adaptive optics SLO apparatus has an adaptive optics system which includes a wavefront sensor and a wavefront correction device. The wave front sensor measures in real time wavefront aberrations caused by the eye being examined, and the wavefront correction device corrects the wavefront aberration with regard to the measurement light and the returning light. This enables the acquisition of SLO images with high resolution in the horizontal or main-scanning direction so that a high-magnification image can be acquired.
Such a high resolution SLO image can be acquired as a moving image. In order to noninvasively observe the dynamics of blood flow (hemodynamics), for example, retinal blood vessels are extracted from each frame of an SLO image, and the moving speed of blood cells through capillaries and so forth is measured by performing image analysis. Also, in order to evaluate the visual function of an eye using an SLO image, photoreceptors P are detected, and the density distribution and arrangement (array) of the photoreceptors P are calculated.
However, confocal images taken of the inner layers of the retina have intense noise signals due to the influence of light reflecting from the nerve fiber layer, and there have been cases where observing blood vessel walls and detection of wall boundaries has been difficult. Accordingly, as of recent, techniques have come into use for observation of non-confocal images obtained by acquiring scattered light, by changing the diameter, shape, and position of a pinhole on the near side of the light receiving portion. An example of this technique is described in Sulai, Dubra et al.; “Visualization of retinal vascular structure and perfusion with a nonconfocal adaptive optics scanning light ophthalmoscope”, J. Opt. Soc. Am. A, Vol. 31, No. 3, pp. 569-579, 2014 (hereinafter “Sulai and Dubra”). Non-confocal images have a great depth of focus, so objects that have unevenness in the depth direction, such as blood vessels can be easily observed, and also noise is reduced since reflected light from the nerve fiber layer is not readily directly received. While observation of photoreceptors at the outer layers of the retina has primarily involved imaging confocal images of the outer segment of photoreceptors, it has been found that the unevenness of the inner segment of photoreceptors can be imaged in non-confocal images. This is described in Scoles, Dubra et al.; “In vivo Imaging of Human Cone Photoreceptor Inner Segment”, IOVS, Vol. 55, No. 7, pp. 4244-4251, 2014 (hereinafter “Scoles and Dubra”). Sulai and Dubra disclose technology for acquiring non-confocal images of retinal blood vessels using an adaptive optics SLO apparatus, while Scoles and Dubra disclose technology for acquiring both confocal images and non-confocal images at the same time using an adaptive optics SLO apparatus. However, these known techniques lack a method of efficiently processing and analyzing confocal images and non-confocal images to accurately determine whether the confocal image and the non-confocal image yields better imaging results.